Magnetoresistive random access memories (MRAMs) may combine magnetic components with standard silicon-based microelectronics to achieve non-volatile memories. For example, silicon based microelectronics include electronic devices such as transistors (e.g., field effect transistors or bipolar transistors), diodes, resistors, interconnect, capacitors or inductors. Other MRAMs may comprise magnetic components with other semiconductor components, for example, components comprising gallium arsenide (GaAs), germanium or other semiconductor material.
An MRAM memory cell comprises a magnetoresistive structure that stores a magnetic moment that is switched between two directions corresponding to two data states (“1” and “0”). In an MRAM cell, information is stored in magnetization directions of a free magnetic layer. In a conventional spin-transfer MRAM memory cell, the data state is programmed to a “1” or to a “0” by forcing a write current directly through the stack of layers of materials that make up the MRAM cell. Generally speaking, the write current, which is spin polarized by passing through one layer, exerts a spin torque on a subsequent free magnetic layer. The torque switches the magnetization of the free magnetic layer between two stable states depending upon the polarity of the write current.